The left property sets the physical distance of how far the left content edge of an
element is to the right from the left content edge of the containing block.

A containing block is simply an element that contains one or more related elements.

There are three other properties that allow you to set the distance for the bottom, right,
and top content edges.
All four properties are used in conjunction with the position property.
Note that if the position property is set to the static value, setting the left
property has no effect.

auto

The auto value dictates that the browser sets the distance between the left content edges.

length

The length value sets the distance between the left content edges and can be in any of the
following seven units.
Use the abbreviation.

Length

Abbrev.

centimeters

cm

ems

em

inches

in

millimeters

mm

picas

pc

pixels

px

points

pt

percentage

The percentage value sets the distance between the left content edges as a percentage of the overall width
of the parent block.
It is a positive integer number.
The percent sign is mandatory.